How to calculate initiative

Hello everybody.

I'm facing a problem with initiative. During my last game session, my PC's were involved in a fight with some thieves. We started the fight, but I was quite embarassed when I realized that I did'nt know how to calculate initiative for casters.

Warriors, ok, it's in the obstacles chapter.
Fast-casting is ok too, it's in the spellcasting options.

But what about a magus who wants to cast a spell without fastcasting it ?

Thanks for your help.

Only their Quickness score contributes ti Initiative.

AS Marko says, It's on page 174

Thank you. I passed too quickly on this page last night...